Handling multiple event triggers

It would be good to trigger actions based of occurrences of events in a given timeframe. For example, 5 fatals in 1 minute, etc.

Due to the endpoints being used for multiple projects, one occurrence would depend on the data, one interface could be something like:

```PHP
Notify_Humans()->if_event( 'cloudwatch' ).matching_pattern( function( $data ) {
    return $data['instance'] === 'wpremote';

} ).occurrences_in_time( 10, '5 minutes' ).then_action(  function() {
   ...
} );
```

`if_event`, `matching_pattern` and `occurrences_in_time` are all "filtering" methods for events